1. Field of the Invention
The present invention relates to a consumable-electrode gas-shield arc welding method and a consumable-electrode gas-shield arc welding system that uses a consumable electrode wire and a conductively-heated filler wire.
2. Description of the Related Art
Recently, in the manufacturing industry, efforts have been made to reduce work periods and costs, and there has been an increasing need for improving the efficiency of consumable-electrode gas-shield arc welding. In a consumable-electrode gas-shield arc welding method using one electrode wire, an increase in the wire melting speed to improve efficiency frequently causes various problems, such as the generation of a large amount of spatter, unstableness in the arc due to a variation in the wire feeding rate, formation of an irregular bead due to the deepening of the welding pool, and the occurrence of welding failures. Therefore, there is a limit in increasing the wire melting rate to improve weldability and efficiency.
A hot-wire gas metal arc (GMA) welding method, which is a consumable-electrode gas-shield arc welding method using two consumable electrode wires (hereinafter, referred to as “two electrode wires”) improves efficiency of arc welding by forming a welding pool by generating an arc with a consumable electrode wire and inserting a conductively-heated filler wire into the welding pool.
As techniques employing such a hot-wire GMA welding method, for example, the following techniques are proposed. Japanese Unexamined Patent Application Publication No. 3-275280 proposes a welding method of generating an arc with a leading consumable electrode wire by inserting two wires into a shield gas nozzle, inserting a trailing filler wire into a molten pool, and branching part of the welding current flowing from the consumable electrode wire to the base metal to the filler wire so as to merge this branching current to a ground terminal of the welding power supply. By using such a welding method, currents flow in opposite directions through the closely disposed consumable electrode wire and filler wire, and thus the arc is constantly directed forward, enabling a sufficient melting depth during high-speed welding.
Japanese Unexamined Patent Application Publication No. 2008-055506 proposes a two-welding-wire-feed arc welding method that speeds up the cooling of a molten pool and the filling of molten metal by generating an arc at a leading consumable electrode wire and inserting a non-energized trailing filler wire into the molten pool. By using such a welding method, the formation of irregular beads due to, for example, undercut and humping can be prevented in high-speed welding of a lap joint.